Display device with touch sensor

ABSTRACT

A common electrode for a display, which is originally provided in a liquid crystal display element, is also used as one (drive electrode) of a pair of electrodes for a touch sensor, and the other (detection-electrode-for-the-sensor) of the pair of electrodes is newly formed. An existing common drive signal as a drive signal for display is used in common for a drive signal for the touch sensor. A capacitance is formed between the common electrode and the detection-electrode-for-the-sensor, and touch detection is performed by utilizing a change of this capacitance caused by a finger touch of a user. Thus, a display device with a touch sensor is also applicable to a mobile device in which electric potential of the user is inconstant in many cases. The newly-provided electrode is only the detection-electrode-for-the-sensor, and it is unnecessary to newly prepare a drive signal for the touch sensor.

RELATED APPLICATION DATA

This application is a continuation of U.S. patent application Ser. No.14/302,481 filed Jun. 12, 2014, which is a continuation of U.S. patentapplication Ser. No. 12/601,310 filed Nov. 23, 2009, now U.S. Pat. No.8,786,557 issued on Jul. 22, 2014, which is a 371 National Stage ofPCT/JP2009/055949 filed Mar. 25, 2009, the entireties of which areincorporated herein by reference to the extent permitted by law. Thepresent application claims the benefit of priority to Japanese PatentApplication No. JP 2008-087739 filed on Mar. 28, 2008 in the JapanPatent Office, the entirety of which is incorporated by reference hereinto the extent permitted by law.

TECHNICAL FIELD

The present invention relates to a display device such as a liquidcrystal display device, and particularly relates to a display devicewith a touch sensor, which includes a touch sensor of capacitance typecapable of inputting information by being touched with a user's fingeror the like.

BACKGROUND ART

In recent years, a display device capable of inputting information bybeing provided with a contact detection device (hereinafter, referred toas a touch sensor), a so-called touch panel, directly mounted on aliquid crystal display device, and displaying various buttons on theliquid crystal display device, in substitution for typical buttons, hasattracted attention. In the tendency that screens of mobile devicesincrease in size, this technique enables common arrangement of a displayand buttons, and this brings a great merit such as space saving andreduction in the number of parts. However, in this technique, there isan issue that the thickness of a whole liquid crystal module increases,since the touch panel is mounted. In particular, in the application tothe mobile devices, since a protective layer is necessary for preventingscratches on the touch panel, there is an issue that the thickness ofthe liquid crystal module tends to increase more and more, and this goesagainst the trend of thinning.

Thus, for example, in Patent document 1, proposed is a liquid crystaldisplay element with a touch panel, in which a conductive film for thetouch panel is provided between a substrate on an observation side ofthe liquid crystal display element and a polarizing plate forobservation arranged on an outer surface of the substrate on theobservation side, and the touch panel of a capacitance type, using anouter surface of the polarizing plate as a touch face, is formed betweenthis conductive film for the touch panel and the outer surface of thepolarizing plate. Thereby, thinning is realized.

Patent document 1: Japanese Unexamined Patent Application PublicationNo. 2008-9750

DISCLOSURE OF THE INVENTION

However, in the liquid crystal display element with the touch paneldisclosed in Patent document 1, it is theoretically necessary for theconductive film for the touch panel to have electric potential identicalto that of a user, and it is necessary for the user to be propertygrounded. Thus, although the application to stationary televisionreceivers which take electric power source from outlets or the like isnot an issue, it is practically difficult to apply the liquid crystaldisplay element with the touch panel to mobile devices. Moreover, in thetechnique described above, since it is necessary for the conductive filmfor the touch panel to be extremely close to the user's finger, anarrangement region of the conductive film for the touch panel islimited, and it is difficult to dispose the conductive film for thetouch panel in, for example, a portion deep inside the liquid crystaldisplay element. That is, design flexibility is low. Moreover, in thetechnique described above, because of the configuration, a circuitsection such as a touch panel drive section and a coordinate detectionsection is necessarily provided, separately from a display drive circuitsection of the liquid crystal display element, and it is difficult tointegrate the circuits of the whole device.

In view of the foregoing, it is a first object of the present inventionto provide a display device with a touch sensor particularly suitablefor a mobile-device application. It is a second object of the presentinvention to provide the display device with the touch sensor havinghigh design flexibility. It is a third object of the present inventionto provide the display device with the touch sensor having aconfiguration in which circuits are easily integrated.

A display device with a touch sensor of the present invention includes:a plurality of display pixel electrodes; a common electrode facing thedisplay pixel electrode; a display function layer having an imagedisplay function; a display control circuit performing an image displaycontrol through applying a voltage for display between each of thedisplay pixel electrode and the common electrode, based on an imagesignal, so that the display function of the display function layer isexhibited; and a touch detection electrode disposed oppositely to thecommon electrode, or beside the common electrode, the touch detectionelectrode and the common electrode forming a capacitance therebetween.

In the display device with the touch sensor of the present invention,the capacitance is formed between the common electrode which isoriginally provided for application of the drive voltage for display,and the touch detection electrode which is newly provided. Thiscapacitance changes depending on presence or absence of a contact by anobject. Therefore, when the drive voltage for display applied to thecommon electrode by the display control section is utilized (also used)as a drive signal for the touch sensor, a detection signal in accordancewith the change of the capacitance is obtained from the touch detectionelectrode. When this detection signal is input to the touch detectioncircuit, it is possible to detect presence or absence of the contact bythe object. Moreover, when the touch detection electrode is divided to aplurality of electrode patterns, and the plurality of electrode patternsare individually driven, it is possible to detect the contact positionof the object. As the display function layer, for example, a liquidcrystal layer is used.

In the display device with the touch sensor of the present invention,such a configuration is possible that an opposed substrate facing acircuit substrate in which the display control circuit is formed isdisposed, the display pixel electrode is disposed on a side close to theopposed substrate, on the circuit substrate, the common electrode isdisposed on a side close to the circuit substrate, on the opposedsubstrate, and the display function layer is disposed to be insertedbetween the display pixel electrode in the circuit substrate and thecommon electrode on the opposed substrate. This configuration issuitable, for example, to the case where the display function layer ismade of liquid crystal of TN (twisted nematic) mode, VA (verticalalignment) mode, or the like. In this case, the touch detectionelectrode is preferably formed on the facing electrode side, and thetouch detection circuit is preferably formed in the circuit substrate.

Also, in the display device with the touch sensor of the presentinvention, such a configuration is possible that an opposed substratefacing the circuit substrate in which the display control circuit and isformed is disposed, the common electrode and the display pixel electrodeare stacked in order with an insulating layer in between, on the circuitsubstrate, and the display function layer is disposed to be insertedbetween the display pixel electrode on the circuit substrate and theopposed substrate. This configuration is suitable to, for example, thecase where the display function layer is made of liquid crystal of aso-called lateral electric field mode such as FFS (fringe fieldswitching) mode. In this case, the touch detection electrode may beformed on the opposed substrate side, or the circuit substrate side. Thetouch detection circuit is preferably formed in the circuit substrate.In the case where the touch detection electrode is formed on the circuitsubstrate side, the common electrode may be disposed inside a displayregion in the circuit substrate, and the touch detection electrode maybe formed to be an electrode layer in a layer level same as that of thecommon electrode, in a frame region surrounding the display region onthe circuit substrate, away from the common electrode. In the case wherethe touch detection electrode is formed on the opposed substrate side,and the touch detection circuit is formed in the circuit substrate, aconductive path may be formed to connect between the touch detectionelectrode on the opposed substrate, and the touch detection circuit inthe circuit substrate. Alternatively, a capacity coupling path may beformed to establish capacitive coupling between the touch detectionelectrode on the opposed substrate, and the touch detection circuit inthe circuit substrate.

According to the display device with the touch sensor of the presentinvention, the capacitance is formed between the common electrode whichis originally provided for application of the drive voltage for display,and the touch detection electrode which is newly provided, and the touchdetection is performed by utilizing the change of the capacitance causedby the contact of the object (finger of the user). Thus, it is possibleto obtain the display device with the touch sensor capable of beingsuitably applied even to a mobile device in which electric potential ofthe user is indefinite in many cases. In particular, when the existingdrive voltage for display which is originally prepared to be applied tothe common electrode for display is utilized (also used) as the drivesignal for the touch sensor, it is possible to obtain the detectionsignal in accordance with the change of the capacitance, from the touchdetection electrode, and thus it is unnecessary to prepare a new drivesignal for the sensor. Moreover, when the touch detection electrode isdivided to the plurality of electrode patterns, and the plurality ofelectrode patterns are individually driven, it is possible to detect thetouched position.

Also, according to the display device with the touch sensor of thepresent invention, it may be arbitrarily selected whether the touchdetection electrode is formed on the opposed substrate side, or on thepixel substrate side, in accordance with the type of the displayfunction layer. Therefore, it is possible to obtain the display devicewith the touch sensor in which design flexibility is high.

Also, according to the display device with the touch sensor of thepresent invention, it is also possible to form the touch detectionelectrode on the circuit substrate side, depending on the type of thedisplay function layer. Thus, in the configuration design, it isadvantageous to form the touch detection circuit in the circuitsubstrate, and it becomes easy to integrally collect the circuit fordisplay and the circuit for the sensor on one circuit substrate. Thatis, integration of the circuits is easy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Views for explaining an operational principle of a display devicewith a touch sensor according to the present invention, and viewsindicating a finger-untouched state.

FIG. 2 Views for explaining an operational principle of the displaydevice with the touch sensor according to the present invention, andviews indicating a finger-touched state.

FIG. 3 A view for explaining an operational principle of the displaydevice with the touch sensor according to the present invention, and aview indicating an example of a waveform of a drive signal and adetection signal of the touch sensor.

FIG. 4 A cross-sectional view illustrating the schematic cross-sectionalconfiguration of the display device with the touch sensor according to afirst embodiment of the present invention.

FIG. 5 A perspective view indicating an example of the configuration ofa main part (a common electrode and a detection-electrode-for-a-sensor)of the display device with the touch sensor illustrated in FIG. 4.

FIG. 6 A circuit view indicating an example of the configuration of adetection circuit in the display device with the touch sensorillustrated in FIG. 4.

FIG. 7 A perspective view indicating another example of theconfiguration of the main part (the common electrode and thedetection-electrode-for-the-sensor) of the display device with the touchsensor illustrated in FIG. 4.

FIG. 8 A perspective view indicating still another example of theconfiguration of the main part (the common electrode and thedetection-electrode-for-the-sensor) of the display device with the touchsensor illustrated in FIG. 4.

FIG. 9 A cross-sectional view illustrating the schematic cross-sectionalconfiguration of the display device with the touch sensor according to asecond embodiment of the present invention.

FIG. 10 Enlarged perspective views of the main part of the displaydevice with the touch sensor illustrated in FIG. 9.

FIG. 11 Cross-sectional views for explaining operation of the displaydevice with the touch sensor illustrated in FIG. 9.

FIG. 12 A cross-sectional view indicating a specific example of theconfiguration of the display device with the touch sensor illustrated inFIG. 9.

FIG. 13 A cross-sectional view indicating a modification of the displaydevice with the touch sensor illustrated in FIG. 9.

FIG. 14 A cross-sectional view indicating another modification of thedisplay device with the touch sensor illustrated in FIG. 9.

FIG. 15 A cross-sectional view indicating a specific example of theconfiguration of the display device with the touch sensor illustrated inFIG. 14.

FIG. 16 A cross-sectional view illustrating the schematiccross-sectional configuration of the display device with the touchsensor according to a third embodiment of the present invention.

FIG. 17 A plan view indicating the schematic plan configuration of thedisplay device with the touch sensor illustrated in FIG. 16.

FIG. 18 A cross-sectional view of the main part, indicating amodification of the display device with the touch sensor illustrated inFIG. 16.

FIG. 19 A schematic cross-sectional view indicating another modificationof the display device with the touch sensor illustrated in FIG. 16.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention(hereinafter, simply referred to as an embodiment) will be described indetail with reference to drawings.

First, with reference to FIGS. 1 to 3, the basic principle of a touchdetection method in a display device with a touch sensor of the presentembodiment will be described. This touch detection method is realized asa capacitance type touch sensor, and a capacitive element is configuredby using a pair of electrodes (a drive electrode E1 and a detectionelectrode E2) facing each other with a dielectric D in between, asillustrated in FIG. 1(A). This configuration is illustrated as anequivalent circuit in FIG. 1(B). A capacitive element C1 is configuredwith the drive electrode E1, the detection electrode E2, and thedielectric D. In the capacitive element C1, one end is connected to anAC signal source S, and the other end P is grounded through a resistanceR and connected to a voltage detector DET. When an AC rectangular waveSg (FIG. 3(B)) with a predetermined frequency (for example,approximately several kHz to ten-odd kHz) is applied from the AC signalsource S to the drive electrode E1 (one end of the capacitive elementC1), an output waveform (detection signal Vdet) as illustrated in FIG.3(A) appears in the detection electrode E2 (other end P of thecapacitive element C1). In addition, this AC rectangular wave Sgcorresponds to a common drive signal Vcom, which will be describedlater.

In a finger-untouched state, as illustrated in FIG. 1, withcharge/discharge to the capacitive element C1, a current I0 inaccordance with a capacity of the capacitive element C1 flows. At thistime, the waveform of electric potential of the other end P in thecapacitive element C1 is, for example, like a waveform V0 of FIG. 3(A),and this is detected with the voltage detector DET.

On the other hand, in a finger-touched state, as illustrated in FIG. 2,a capacitive element C2 formed by the finger is added in series to thecapacitive element C1. In this state, with the charge/discharge to thecapacitive elements C1 and C2, currents I1 and I2 flow, respectively. Atthis time, the waveform of the electric potential of the other end P inthe capacitive element C1 is, for example, like a waveform V1 of FIG.3(A), and this is detected with the voltage detector DET. At this time,the electric potential at the point P is an electric partial potentialdefined by the values of the currents I1 and I2 flowing through thecapacitive elements C1 and C2, respectively. Therefore, the waveform V1becomes a value smaller than that of the waveform V0 in the untouchedstate. As will be described later, the voltage detector DET compares thedetected voltage with a predetermined threshold voltage Vth. When thedetected voltage is equal to or smaller than the threshold voltage, thevoltage detector DET determines that it is in the untouched state. Onthe other hand, when the detected voltage is equal to or larger than thethreshold voltage, the detector DET determines that it is in the touchedstate. In this manner, it is possible to perform the touch detection.

First Embodiment

FIG. 4 illustrates the cross-sectional configuration of a main part ofthe display device with the touch sensor of the present embodiment. Inthis display device with the touch sensor, a liquid crystal displayelement is used as a display element, and a part of an electrode (commonelectrode 43, which will be described later) which is originallyprovided in this liquid crystal display element, and a drive signal fordisplay (common drive signal Vcom, which will be described later) areused also for another purpose, thereby the capacitance type touch sensoris configured.

As illustrated in FIG. 4, the display device with the touch sensorincludes a pixel substrate 2, an opposed substrate 4 facing this pixelsubstrate 2, and a liquid crystal layer 6 inserted between the pixelsubstrate 2 and the opposed substrate 4.

The pixel substrate 2 includes a TFT substrate 21 as a circuitsubstrate, and a plurality of pixel electrodes 22 disposed in a matrixform on this TFT substrate 21. In addition to a display driver and TFTs(thin film transistor), which are not illustrated in the figure, fordriving each of the pixel electrodes 22, wirings such as a source linesupplying a pixel signal to each of the pixel electrodes, and a gateline driving each of the TFTs are formed in the TFT substrate 21.Moreover, in the TFT substrate 21, a detection circuit (FIG. 6)performing touch detection operation, which will be described later, mayalso be formed.

The opposed substrate 4 includes a glass substrate 41, a color filter 42formed on one surface of this glass substrate 41, and a common electrode43 formed on this color filter 42. The color filter 42 is configured,for example, by aligning color filter layers of three colors, red (R),green (G), and blue (B), in a cycle, and a set of three colors of R, G,and B is assigned to each display pixel (pixel electrode 22). The commonelectrode 43 is also used as a drive electrode for the sensor whichconstitutes a part of the touch sensor performing the touch detectionoperation, and corresponds to the drive electrode E1 in FIG. 1.

The common electrode 43 is coupled to the TFT substrate 21 with acontact conductive pillar 7. The common drive signal Vcom having an ACrectangular waveform is applied from the TFT substrate 21 to the commonelectrode 43 through this contact conductive pillar 7. This common drivesignal Vcom defines the pixel voltage applied to the pixel electrode 22as well as a display voltage of each of the pixels, and is also used asthe drive signal for the touch sensor. The common drive signal Vcomcorresponds to the AC rectangular wave Sg supplied from the drive signalsource S of FIG. 1.

On the other surface of the glass substrate 41, adetection-electrode-for-a-sensor 44 is formed. Moreover, on thisdetection-electrode-for-the-sensor 44, a polarizing plate 45 isdisposed. The detection-electrode-for-the-sensor 44 constitutes a partof the touch sensor, and corresponds to the detection electrode E2 inFIG. 1.

The liquid crystal layer 6 modulates light passing through the liquidcrystal layer 6, in accordance with the state of the electric field, andis made of liquid crystal of various modes, for example, TN (twistednematic), VA (vertical alignment), and ECB (electrically controlledbirefringence).

An alignment film is disposed between the liquid crystal layer 6 and thepixel substrate 2, and between the liquid crystal layer 6 and theopposed substrate 4, respectively. Although a polarizing plate on alight incident side is disposed below the pixel substrate 2, itsillustration is omitted in the figure.

FIG. 5 perspectively illustrates an example of the configuration of thecommon electrode 43 and the detection-electrode-for-the-sensor 44 in theopposed substrate 4. In this example, the common electrode 43 is dividedto a plurality of stripe-shaped electrode patterns extending in theright-and-left direction of the figure. With a driver 43D, the commondrive signal Vcom is sequentially supplied to each of the electrodepatterns, and the line-sequential scanning drive is time-divisionallyperformed. On the other hand, the detection-electrode-for-the-sensor 44is configured with a plurality of stripe-shaped electrode patternsextending in a direction orthogonal to the extending direction of theelectrode patterns in the common electrode 43. The detection signal Vdetis output from each of the electrode patterns in thedetection-electrode-for-the-sensor 44, and input to a detection circuit8 illustrated in FIG. 6.

FIG. 6 illustrates an example of the configuration of the detectioncircuit 8 performing the touch detection operation. This detectioncircuit 8 includes an operational amplifier 81 for signal amplification,a low pass filter (LPF) 82 which cuts a higher-frequency component, andallows a lower-frequency component to pass, and a high pass filter (HPF)83 which allows the high-frequency component to pass, a rectifyingsmoothing section 84, and a comparator 85. An input terminal Tin isconnected to a positive input terminal (+) of the operational amplifier81, and the detection signal Vdet is input to the input terminal Tin. Anoutput terminal of the operational amplifier 81 is connected to therectifying smoothing section 84 through the LPF 82. The HPF 83 isconnected to the LPF 82. The LPF 82 has the configuration in which aresistance 82R and a capacitor 82C are connected in parallel, and theHPF 83 has the configuration in which a resistance 83R and a capacitor83C are connected in series between the ground and the LPF 82. Aconnection point of the LPF 82 and the HPF 83 is connected to a negativeinput terminal (−) of the operational amplifier 81. The rectifyingsmoothing section 84 includes a rectifying section made of a half-waverectification diode 84D, and a smoothing section in which a resistance84R and a capacitor 82C are connected in parallel between the ground andthe half-wave rectification diode 84D. An output terminal of therectifying smoothing section 84 is connected to a positive inputterminal (+) of the comparator 85. The predetermined threshold voltageVth (refer to FIG. 3) is input to a negative input terminal (−) of thiscomparator 85. An output terminal of the comparator 85 is connected toan output terminal Tout, and a detected result (touched or not) isoutput from the output terminal Tout.

The detection circuit 8 having such a configuration operates as follows.The detection signal Vdet input to the input terminal Tin is amplifiedwith the operational amplifier 81. Then, the low-frequency component inthe detection signal Vdet passes through the LPF 82, and thehigh-frequency component is removed through the HPF 83. Thelow-frequency AC element passing through the LPF 82 is half-waverectified with the diode 84D in the rectifying smoothing section 84, andthen smoothed to a level signal and input to the comparator 85. Thecomparator 85 compares the input level signal with the threshold voltageVth. When the input level signal is equal to or smaller than thethreshold voltage Vth, the comparator 85 outputs a touch detectionsignal.

The detection circuit 8 may be formed in a peripheral region (anon-display region or a frame region) on the opposed substrate 4.Alternatively, the detection circuit 8 may be formed in a peripheralregion on the pixel substrate 2. However, when the detection circuit 8is formed on the pixel substrate 2, integration of the detection circuit8 and various circuit elements for display control or the like, whichare originally formed on the pixel substrate 2, is realized, and this ispreferable from a viewpoint of simplification of the circuit realized bythe integration. In this case, each of the electrode patterns in thedetection-electrode-for-the-sensor 44 and the detection circuit 8 of thepixel substrate 2 are connected with a contact conductive pillar (notillustrated in the figure) which is similar to the contact conductivepillar 7, and the detection signal Vdet may be transmitted from thedetection-electrode-for-the-sensor 44 to the detection circuit 8.

Next, operation of the display device with the touch sensor having theabove configuration will be described.

The display driver (not illustrated in the figure) in the pixelsubstrate 2 line-sequentially supplies the common drive signal Vcom toeach of the electrode patterns in the common electrode 43. The displaydriver also supplies the pixel signal to the pixel electrode 22 throughthe source line, and line-sequentially controls switching of the TFT ineach of the pixel electrodes through the gate line, in synchronizationwith the supply of the pixel signal. Thereby, the electric field isapplied to the liquid crystal layer 6 for each pixel, in thelongitudinal direction (direction perpendicular to the substrate)defined by the common drive signal Vcom and each of the pixel signals,and the liquid crystal state is modulated. In this manner, the displayis performed with a so-called inversion drive.

On the other hand, on the opposed substrate 4 side, the capacitiveelement C1 is formed at each intersection portion of each of theelectrode patterns in the common electrode 43 and each of the electrodepatterns in the detection-electrode-for-the-sensor 44. When the commondrive signal Vcom is time-divisionally sequentially applied to each ofthe electrode patterns in the common electrode 43, the charge/dischargeis performed on each of the capacitive elements C1 of one line formed atthe intersection portion of the electrode pattern in the commonelectrode 43, to which the common drive voltage Vcom is applied, andeach of the electrode patterns in the detection-electrode-for-the-sensor44. As a result, the detection signal Vdet with the magnitude inaccordance with the capacity of the capacitive element C1 is output fromeach of the electrode patterns in the detection-electrode-for-the-sensor44. Under the conditions where the user's finger is not in contact withthe surface of the opposed substrate 4, the magnitude of this detectionsignal Vdet is approximately constant. A line of the capacitive elementsC1 to be charged/discharged is line-sequentially shifted by the scanningwith the common drive signal Vcom.

Here, when the user's finger touches any place on the surface of theopposed substrate 4, the capacitive element C2 by the finger is added tothe capacitive element C1, which is originally formed in that touchedplace. As a result, the value of the detection signal Vdet when thattouched place is scanned (that is, in the electrode patterns of thecommon electrode 43, when the common drive signal Vcom is applied to theelectrode pattern which is corresponding to that touched place) becomessmall, in comparison with the detection signal Vdet of other places. Thedetection circuit 8 (FIG. 6) compares this detection signal Vdet withthe threshold voltage Vth. When the detection signal Vdet is equal to orsmaller than the threshold voltage Vth, the detection circuit 8determines that place as the touched place. This touched place may bedetermined with the application timing of the common drive signal Vcom,and the detection timing of the detection signal Vdet which is equal toor smaller than the threshold voltage Vth.

In this manner, according to the present embodiment, the capacitancetype touch sensor has the configuration in which the common electrode43, which is originally provided in the liquid crystal display element,is also used as one of the pair of electrodes for the touch sensor,including the drive electrode and the detection electrode, and thecommon drive signal Vcom as the drive signal for display is used incommon for the drive signal for the touch sensor. Thus, thenewly-provided electrode is only the detection-electrode-for-the-sensor44, and it is unnecessary to newly prepare the drive signal for thetouch sensor. Therefore, the configuration is simple.

Also, in the display device with the touch panel of the related art(Patent document 1), the magnitude of a current flowing through a sensoris accurately measured, and a touched position is determined withanalogue computation, based on that measured value. On the other hand,in the present embodiment, the presence or absence of the relativechange in the current (change in electric potential) in accordance withthe presence or absence of the touch may be digitally detected, and itis possible to improve the detection accuracy with the simple detectioncircuit configuration. Moreover, the capacitance is formed between thecommon electrode 43, which is originally provided for application of thecommon drive signal Vcom, and the detection-electrode-for-the-sensor 44,which is newly provided, and the touch detection is performed byutilizing the change of this capacitance caused by the finger touch ofthe user. Thus, the display device with the touch panel may be appliedeven to a mobile device in which electric potential of the user isinconstant in many cases.

Also, since the detection-electrode-for-the-sensor 44 is divided to theplurality of electrode patterns, and the plurality of electrode patternsare individually time-divisionally driven, it is also possible to detectthe touched position.

In addition, in the above description, as illustrated in FIG. 5,although both the common electrode 43 and thedetection-electrode-for-the-sensor 44 are formed as the plurality ofelectrode patterns extending so as to intersect each other, they are notlimited to this. For example, as illustrated in FIG. 7, the commonelectrode 43 may be formed as a single electrode extending all over, andthe detection-electrode-for-the-sensor 44 may be formed as a pluralityof individual electrodes disposed in a matrix form. In this case, it ispossible to immediately determine the touched position with thedetection signal Vdet from each of the individual electrodesconstituting the detection-electrode-for-the-sensor 44.

Alternatively, as illustrated in FIG. 8, the common electrode 43 may beformed as a plurality of electrode patterns divided in a stripe shape,similarly to FIG. 5, and the detection-electrode-for-the-sensor 44 maybe formed as a plurality of individual electrodes disposed in a matrixform, similarly to FIG. 7. Also in this case, it is possible to performthe detection while sequentially scanning the plurality of electrodepatterns in the common electrode 43 with the common drive signal Vcom.

Second Embodiment

Next, a second embodiment will be described. The present embodimentdiffers from the above-described first embodiment in that a liquidcrystal element of a lateral electric field mode is used as a displayelement.

FIG. 9 illustrates the cross-sectional configuration of the main part ofthe display device with the touch sensor according to the presentembodiment, and FIG. 10 illustrates its perspective configuration. Inthese views, same reference numerals as in FIG. 4 are used to indicateidentical components, and thereby the description is appropriatelyomitted.

The display device with the touch sensor according to the presentembodiment includes a pixel substrate 2A, an opposed substrate 4A facingthis pixel substrate 2A, and the liquid crystal layer 6 inserted betweenthe pixel substrate 2A and the opposed substrate 4A.

The pixel substrate 2A includes the TFT substrate 21, the commonelectrode 43 disposed on this TFT substrate 21, and the plurality ofpixel electrodes 22 disposed in a matrix form on the this commonelectrode 43 with an insulating layer 23 in between. In addition to thedisplay driver and the TFTs, which are not illustrated in the figure,for driving each of the pixel electrodes 22, wirings such as the sourceline supplying the pixel signal to each of the pixel electrodes, and thegate line driving each of the TFTs are formed in the TFT substrate 21.Moreover, the detection circuit (FIG. 6) performing the touch detectionoperation is formed in the TFT substrate 21. The common electrode 43 isalso used as the driving electrode for the sensor which constitutes apart of the touch sensor performing the touch detection operation, andcorresponds to the driving electrode E1 in FIG. 1.

The opposed substrate 4A includes the glass substrate 41, and the colorfilter 42 formed on one surface of this glass substrate 41. On the othersurface of the glass substrate 41, thedetection-electrode-for-the-sensor 44 is formed. Moreover, on thisdetection-electrode-for-the-sensor 44, the polarizing plate 45 isdisposed. The detection-electrode-for-the-sensor 44 constitutes a partof the touch sensor, and corresponds to the detection electrode E2 inFIG. 1. The detection-electrode-for-the-sensor 44 is divided to theplurality of electrode patterns, as illustrated in FIG. 5, FIG. 7 orFIG. 8. The detection-electrode-for-the-sensor 44 may be formed directlyon the opposed substrate 4A, through the use of thin film process, ormay be formed indirectly. In this case, a touch detection electrode 44is formed on a film substrate which is not illustrated in the figure,and the film substrate on which this touch detection electrode 44 isformed may be attached to the surface of the opposed substrate 4A. Inthis case, it is possible to attach the film substrate to not onlybetween the glass and the polarizing plate, but also the top surface ofthe polarizing plate. The film substrate may be formed in a filmconstituting the polarizing plate.

The common drive signal Vcom having the AC rectangular waveform isapplied from the TFT substrate 21 to the common electrode 43. Thiscommon drive signal Vcom defines the pixel voltage applied to the pixelelectrode 22 as well as the display voltage of each of the pixels, andis also used as the drive signal for the touch sensor. The common drivesignal Vcom corresponds to the AC rectangular wave Sg supplied from thedrive signal source S of FIG. 1.

The liquid crystal layer 6 modulates the light passing through theliquid crystal layer 6, in accordance with the state of the electricfield, and is made of liquid crystal of a lateral electric field mode,for example, FFS (fringe field switching) mode, and IPS (in-planeswitching) mode.

The configurations of the common electrode 43 in the pixel substrate 2A,and the detection-electrode-for-the-sensor 44 in the opposed substrate4A are, for example, similar to those illustrated in FIG. 5, and boththe common electrode 43 and the detection-electrode-for-the-sensor 44are formed as the plurality of electrode patterns extending so as tointersect each other. However, the configurations of the commonelectrode 43 and the detection-electrode-for-the-sensor 44 may besimilar to those illustrated in FIG. 7 or FIG. 8 described above.

With reference to FIG. 10, a more detailed description will be made. Inthe liquid crystal element of FFS mode as indicated here, the pixelelectrode 22 patterned in a comb shape is disposed on the commonelectrode 43 formed on the pixel substrate 2A, with the insulating layer23 in between, and an alignment film 26 covering the pixel electrode 22is formed. Between this alignment film 26 and an alignment film 46 onthe opposed substrate 4A side, the liquid crystal layer 6 is supported.Two polarizing plates 24 and 45 are disposed in the state ofcross-nichols. The rubbing direction of the two alignment films 26 and46 corresponds to the transmission axis of one of the two polarizingplates 24 and 25. In FIG. 10, the case where the rubbing directioncorresponds to the transmission axis of the polarizing plate 45 on thelight exit side is indicated. Moreover, the rubbing direction of the twoalignment films 26 and 46, and the direction of the transmission axis ofthe polarizing plate 45 are set approximately parallel to the extendingdirection (longitudinal direction of the comb) of the pixel electrode22, in a range where the turning direction of the liquid crystalmolecule is defined.

Next, the operation of the display device with the touch sensor havingthe above configuration will be described.

Here, first, with reference to FIGS. 10 and 11, the display operationprinciple of the liquid crystal element of FFS mode will be simplydescribed. Here, FIG. 11 illustrates the enlarged cross-section of themain part of the liquid crystal element. In these views, (A) illustratesthe state of the liquid crystal element when no electric field isapplied, and (B) illustrates the state of the liquid crystal elementwhen the electric field is applied.

In the state where the voltage is not applied between the commonelectrode 43 and the pixel electrode 22 (FIGS. 10(A) and 11(A)), theaxis of the liquid crystal molecule 61 constituting the liquid crystallayer 6 is orthogonal to the transmission axis of the polarizing plate24 on the light incident side, and becomes parallel to the transmissionaxis of the polarizing plate 45 on the light exit side. For this reason,an incident light h transmitting the polarizing plate 24 on the lightincident side reaches the polarizing plate 45 on the light exit side,without generating a phase difference in the liquid crystal layer 6, andis absorbed in the polarizing plate 45, thereby black is displayed. Onthe other hand, in the state where the voltage is applied between thecommon electrode 43 and the pixel electrode 22 (FIGS. 10(B) and 11(B)),the alignment direction of the liquid crystal molecule 61 is turned inthe oblique direction with respect to the extending direction of thepixel electrode 22, with a lateral electric field E generated betweenthe pixel electrodes. At this time, the electric field intensity whenwhite is displayed is optimized so that the liquid crystal molecule 61located in middle of the thickness direction of the liquid crystal layer6 is turned approximately 45 degrees. Thereby, the phase difference isgenerated in the liquid crystal layer 6 while the incident light htransmits the liquid crystal layer 6, after transmitting the polarizingplate 24 on the light incident side. Thus, the incident light h becomesa straight-line polarized light which is turned 90 degrees, andtransmits the polarizing plate 45 on the light exit side, thereby whiteis displayed.

Next, the display control operation and the touch detection operation ofthe display device with the touch sensor will be described. Theseoperations are similar to those in the first embodiment described above,thereby the descriptions are appropriately omitted.

The display driver (not illustrated in the figure) in the pixelsubstrate 2A line-sequentially supplies the common drive signal Vcom toeach of the electrode patterns in the common electrode 43. The displaydriver also supplies the pixel signal to the pixel electrode 22 throughthe source line, and line-sequentially controls the switching of the TFTin each of the pixel electrodes through the gate line, insynchronization with the supply of the pixel signal. Thereby, theelectric field is applied to the liquid crystal layer 6 for each of thepixels, in the lateral direction (direction parallel to the substrate)defined by the common drive signal Vcom and each of the pixel signals,and the liquid crystal state is modulated. In this manner, the displayis performed with the so-called inversion drive.

On the other hand, on the opposed substrate 4A side, when the commondrive signal Vcom is time-divisionally sequentially applied to each ofthe electrode patterns in the common electrode 43, charge/discharge isperformed on each of the capacitive elements C1 of one line formed atthe intersection portion of the electrode pattern in the commonelectrode 43, to which the common drive voltage Vcom is applied, andeach of the electrode patterns in the detection-electrode-for-the-sensor44. The detection signal Vdet with the magnitude in accordance with thecapacity of the capacitive element C1 is output from each of theelectrode patterns in the detection-electrode-for-the-sensor 44. Underthe conditions where the user's finger is not in contact with thesurface of the opposed substrate 4A, the magnitude of this detectionsignal Vdet is approximately constant. When the user's finger touchesany place on the surface of the opposed substrate 4A, the capacitiveelement C2 by the finger is added to the capacitive element C1 which isoriginally formed in that touched place. As a result, the value of thedetection signal Vdet when that touched place is scanned becomes small,in comparison with the detection signal Vdet in other places. Thedetection circuit 8 (FIG. 6) compares this detection signal Vdet withthe threshold voltage Vth. When the detection signal Vdet is equal to orsmaller than the threshold voltage Vth, the detection circuit 8determines that place as the touched place. This touched place isdetermined with the application timing of the common drive signal Vcom,and the detection timing of the detection signal Vdet which is equal toor smaller than the threshold voltage Vth.

In this manner, according to the present embodiment, similarly to thecase of the above-described first embodiment (FIG. 5), the capacitancetype touch sensor has the configuration in which the common electrode 43which is originally provided in the liquid crystal display element isalso used as one of the pair of electrodes for the touch sensor,including the drive electrode and the detection electrode, and thecommon drive signal Vcom as the drive signal for display is used incommon for the drive signal for the touch sensor. Thus, thenewly-provided electrode is only the detection-electrode-for-the-sensor44, and it is unnecessary to newly prepare a drive signal for the touchsensor. Therefore, the configuration is simple.

In particular, in the present embodiment, since the common electrode 43as the drive electrode for the touch sensor is arranged on the pixelsubstrate 2 side (on the TFT substrate 21), it is extremely easy tosupply the common drive signal Vcom from the TFT substrate 21 to thecommon electrode 43, and necessary circuits and electrode patterns, andwirings or the like may be collected in the pixel substrate 2.Therefore, integration of the circuits is realized. Thus, a supply path(contact conductive pillar 7) of the common drive signal Vcom from thepixel substrate 2 side to the opposed substrate 4 side, which isnecessary in the first embodiment described above (FIG. 5), isunnecessary, and the configuration is more simple.

In addition, although the detection circuit 8 (FIG. 6) may be formed inthe peripheral region (the non-display region or the frame region) onthe opposed substrate 4, the detection circuit 8 is preferably formed inthe peripheral region on the pixel substrate 2. When the detectioncircuit 8 is formed on the pixel substrate 2, integration of thedetection circuit 8 and various circuit elements for display control orthe like, which are originally formed on the pixel substrate 2, isrealized. In this case, for example, as illustrated in FIG. 12, acontact conductive pillar 7A is formed in the peripheral region, and thedetection circuit 8 (not illustrated in the figure) formed in the pixelsubstrate 2, and the surface of the color filter 42 in the opposedsubstrate 4 are connected, thereby forming a capacitive coupling pathbetween the detection-electrode-for-the-sensor 44, and the detectioncircuit 8. The detection signal Vdet may be transmitted from thedetection-electrode-for-the-sensor 44 to the detection circuit 8 throughthis capacitive coupling path. However, in this case, since thedetection-electrode-for-the-sensor 44 is in the floating state, it ispreferable to connect the detection-electrode-for-the-sensor 44 to theground through a high-resistance 10, to avoid this situation. Groundingthe detection-electrode-for-the-sensor 44 in this manner brings a merit,also from the viewpoint of releasing static electric charge to theground.

Modification

In the second embodiment, the detection-electrode-for-the-sensor 44 isprovided on the surface side (side opposite from the liquid crystallayer 6) of the glass substrate 41. However, a modification is possibleas follows.

For example, as illustrated in FIG. 13, thedetection-electrode-for-the-sensor 44 may be provided on the liquidcrystal layer 6 side, in comparison with the color filter 42.

Alternatively, as illustrated in FIG. 14, thedetection-electrode-for-the-sensor 44 is preferably provided between theglass substrate 41 and the color filter 42. In the case of the lateralelectric field mode, when there is the electrode in the verticaldirection, the electric field is applied in the vertical direction, andthe view angle or the like is highly deteriorated due to the rising ofthe liquid crystal. When the detection-electrode-for-the-sensor 44 isdisposed with the dielectric such as the color filter 42 in between,this issue is highly improved. In this case, for example, as illustratedin FIG. 15, the detection circuit 8 (not illustrated in the figure)formed in the pixel substrate 2, and thedetection-electrode-for-the-sensor 44 in the opposed substrate 4 areconnected with a contact conductive pillar 7B. Thereby, a conductivepath is formed between the detection-electrode-for-the-sensor 44, andthe detection circuit 8, and the detection signal Vdet may betransmitted from the detection-electrode-for-the-sensor 44 to thedetection circuit 8 through this conductive path.

Third Embodiment

In the first embodiment and the second embodiment described above, thedetection-electrode-for-the-sensor 44 is disposed in the display region.However, in the present embodiment, as illustrated in FIGS. 16 and 17,the detection-electrode-for-the-sensor 44 is provided in a region (frameregion F) surrounding a display region D. FIG. 17 illustrates the planconfiguration of the display device with the touch sensor of the presentembodiment, and FIG. 16 illustrates the configuration as viewed from thedirection of A-A arrow in FIG. 17.

In this display device with the touch sensor, both the common electrode43 and the detection-electrode-for-the-sensor 44 are formed on a pixelsubstrate 2B side, and none of the common electrode 43 and thedetection-electrode-for-the-sensor 44 are formed on the opposedsubstrate 4 side. Specifically, the common electrode 43 is formed on theTFT substrate 21, in the whole display region D. On the other hand, thedetection-electrode-for-the-sensor 44 is formed on the TFT substrate 21,only in the frame region F. The detection-electrode-for-the-sensor 44 isformed as a plurality of individual electrode groups. Each of theindividual electrodes is, for example, assigned as an operation buttoncorresponding to various functions of the display application. Each ofthe individual electrodes in the detection-electrode-for-the-sensor 44is connected to a detection signal line for the sensor 51 through asource and a drain of a TFT 50 which performs switching by a controlfrom a scanning signal line 52. The scanning signal line 52 and the TFT50 are formed at the same time as formation of the drive circuit of thepixels, and are configured so as to sequentially time-divisionally scaneach of the individual electrodes. Thereby, it is unnecessary to havethe division number of the detection circuits, and this is extremelyefficient.

In the display device with the touch sensor having such a configuration,each of the individual electrodes in thedetection-electrode-for-the-sensor 44 is disposed on the same plane as aformation plane of the common electrode 43, separately from the commonelectrode 43. Thus, the capacitive coupling in the lateral direction isgenerated between each of the individual electrodes in thedetection-electrode-for-the-sensor 44, and the common electrode 43, andthe capacitive element C1 is formed. The common drive signal Vcom isapplied to the common electrode 43 (in the example of FIG. 17, a singleelectrode extending all over), and the TFT 50 is sequentially turned onwith the scanning signal line 52. Thereby, the detection signal Vdet istime-divisionally taken out from each of the individual electrodes inthe detection-electrode-for-the-sensor 44. The taken-out detectionsignal Vdet is input to the detection circuit 8 (not illustrated in FIG.16) having the configuration illustrated in FIG. 6, through thedetection signal line for the sensor 51.

Under the conditions where the user's finger is not in contact with thesurface of an opposed substrate 4D, the magnitude of this detectionsignal Vdet is approximately constant. On the other hand, under theconditions where the user's finger is in contact with any place on thesurface of the opposed substrate 4D (position corresponding to any ofthe individual electrodes in the detection-electrode-for-the-sensor 44),the capacitive element C2 by the finger is added to the capacitiveelement C1 which is originally formed in that touch place. As a result,the value of the detection signal Vdet when that touched place isscanned becomes small. The detection circuit 8 (FIG. 6) compares thisdetection signal Vdet with the threshold voltage Vth. When the detectionsignal Vdet is equal to or smaller than the threshold voltage Vth, thedetection circuit 8 determines that place as the touched place. Thistouched place may be determined with the scanning timing of theindividual electrodes in the detection-electrode-for-the-sensor 44, withthe scanning signal, and the detection timing of the detection signalVdet which is equal to or smaller than the threshold voltage Vth.

In this manner, according to the present embodiment, since both thecommon electrode 43 and the detection-electrode-for-the-sensor 44 aredisposed on the pixel substrate 2 side, it is possible to easily form atransmission path of the common drive signal Vcom between a sensor drivecircuit (not illustrated in the figure) formed in the TFT substrate 21,and the common electrode 43, and a transmission path of the detectionsignal Vdet between the detection-electrode-for-the-sensor 44, and thedetection circuit 8, without the contact conductive pillar in between.Therefore, it is extremely easy to collectively integrate the commonelectrode 43 and the detection-electrode-for-the-sensor 44, the circuitfor display, and the drive circuit and the detection circuit for thetouch sensor, in the TFT substrate 21.

In addition, like the present embodiment, in the case where the commonelectrode 43 and the detection-electrode-for-the-sensor 44 are disposedside by side, and the capacitive element C1 by the capacity coupling inthe lateral direction is formed between the common electrode 43 and thedetection-electrode-for-the-sensor 44, there is a case where a noisetransfer from the common electrode 43 to the circuit element (TFT 50 orthe like) in the TFT substrate 21 becomes an issue. Thus, to preventthis, as illustrated in FIG. 18, it is preferable to provide a shieldelectrode 53 below the detection-electrode-for-the-sensor 44. However,as the above-described shield layer, it is also possible to divert atransparent electrode film constituting a metal wiring and a pixelelectrode, without particularly providing a new special layer.

Modification

In the third embodiment described above, the common electrode 43 and thedetection-electrode-for-the-sensor 44 are disposed side by side on theTFT substrate 21, and the capacitive element C1 is formed by thecapacitive coupling in the lateral direction. However, unlike this, itis also possible to form the capacitive element C1 by the capacitycoupling in the vertical direction. For example, as illustrated in FIG.19, the common electrode 43 extends to not only the display region D onthe TFT substrate 21, but also to the frame region F, and thedetection-electrode-for-the-sensor 44 is formed so as to face the commonelectrode 43 in the frame region F of the TFT substrate 21, thedetection-electrode-for-the-sensor 44 serving as an electrode layer in alayer level different from that of the common electrode 43. Thereby, thecapacitive element C1 is formed between the common electrode 43 and thedetection-electrode-for-the-sensor 44. In this case, a contact pillar 7Cconnecting the detection-electrode-for-the-sensor 44, and the TFTsubstrate 21 is provided, and thereby the detection signal Vdet from thedetection-electrode-for-the-sensor 44 may be transmitted to the TFTsubstrate 21 side.

As it is clear from the descriptions of the first embodiment to thethird embodiment, in accordance with the type of the liquid crystallayer as the display function layer, it may be arbitrarily selectedwhether the detection-electrode-for-the-sensor 44 is formed on theopposed substrate 4 side, or on the pixel substrate 2 side. Therefore,there is a merit that flexibility of the configuration design is high.

Hereinbefore, although the present invention is described with someembodiments, the present invention is not limited to these embodiments,and various modifications are possible. For example, in the secondembodiment and the third embodiment described above, the example of theliquid crystal element of FFS mode as the lateral electric field mode isdescribed. However, similarly to this, the liquid crystal of IPS modemay be applied.

In the embodiments described above, the display device using the liquidcrystal display element as the display element is described. However,the present invention is also applicable to a display device using otherdisplay elements, for example, organic EL elements.

What is claimed is:
 1. A display device comprising: a pixel substrate; acommon electrode disposed on the pixel substrate; a plurality of touchdetecting electrodes configured to detect capacitance variation causedby a touch, the touch detecting electrodes being disposed on the pixelsubstrate in a region surrounding the common electrode; an opposedsubstrate facing the pixel substrate; at least one pixel electrodearranged between the pixel substrate and the opposed substrate; and adisplay function layer interposed between the pixel substrate and theopposed substrate within an image display area, wherein, the commonelectrode and the touch detecting electrodes are coplanar, the pixelelectrode is used to drive the function layer to effect a display of animage, the touch detecting electrodes and the common electrode arecapacitively coupled to each other, the touch detecting electrodes aretime-divisionally scanned, each of the at least one touch detectingelectrode is located outside of the image display area, each of the atleast one touch detecting electrode is located along at least a side ofthe circumference of the image display area, and each of the at leastone touch detecting electrode is located in parallel to at least theside of the circumference of the image display area.
 2. The displaydevice set forth in claim 1, wherein the touch detecting electrodes arelocated at a substantially same interval.
 3. A display devicecomprising: a pixel substrate; a common electrode disposed on the pixelsubstrate; a plurality of touch detecting electrodes configured todetect capacitance variation caused by a touch, the touch detectingelectrodes being disposed on the pixel substrate in a region surroundingthe common electrode; an opposed substrate facing the pixel substrate;at least one pixel electrode arranged between the pixel substrate andthe opposed substrate; and a display function layer interposed betweenthe pixel substrate and the opposed substrate within an image displayarea, wherein, the common electrode and the touch detecting electrodesare coplanar, the pixel electrode is used to drive the function layer toeffect a display of an image, the touch detecting electrodes and thecommon electrode are capacitively coupled to each other, the touchdetecting electrodes are time-divisionally scanned, and a top surface ofthe common electrode and a top surface of the at least one touchdetecting electrode provide a substantially same plane.